Impeller assembly



`June 2l, 1966 D. E. HARRIS 3,257,071

IMPELLER ASSEMBLY Filed June 26, 1964 FVG, FIC?. .3

his A TTQ/PNEYS United States Patent() 3,257,071 IMPELLER ASSEMBLY Dwight E. Harris, Woodstock, N.Y., assignor toRotron Manufacturing Company, Inc., Woodstock, N.Y., a corporation of New York Filed .lune 26, 1964, Ser. No. 378,200 2 Claims. (Cl. 230-134) One method of fabricating impellers of such types is to cast or mold the vanes integrally with the back plate and then secure the shroud'in a suitable manner to the outer free ends of the blades. Although metals are quite satisfactory, for impellers of relatively small size and capacity, a particularly desirable material is plastic because of relatively low cost and its ability to be readily formed and assembled by adhesives or by heat. In either case,

- the impeller is generallyformed of two or more separate elements, one of which may incorporate the vanes and the other of which acts as a shield or shroud to support the vanes and aid in directing the air flow. These elements Vare assembled in a suitable manner to provide the finished impeller. For example, a shroud ycan be connected to vanes cast integrally with a back plate by welding, brazing or soldering, in the case of a metal casting and shroud, or by a suitable adhesive or heat bonding in the case of a plastic casting and shroud. To connect the shroud to the impeller vanes using the foregoing techniques, it is generally necessary to support the casting on a suitable -bracket or jig, position the shroud thereon and hold the shroud in the proper position while the. welding, brazing, glueing or heat bonding is carried out.v

When plastic is used for the impeller parts, the adhesive or cement must carefully be applied to each vane while the casting is suitably supported, and then the shroud must be held in position by suitable clamps until `the adhesive sets. When adhesives are used to install'the shroud, there is always a danger that the shroud will not be in close contact with the impeller vanes at all points Vdue to irregularities or distortions of the parts, and that the bonding may be incomplete or absent in places.

In methods in which heat is applied during interconnection of the vanes and shroud, diiculties due to distortions of the parts because of the expansion and wraping caused by the heating are usually encountered.

Another method of assembling the various elements of the impeller is by means of tabs and slots. For example, tabs may be formed on the vanes, which tabs extend into mating slots formed in the back plate and/ or shroud, and adapted to be bent over to secure the elements together. With this technique, however, it is diicult to obtain accurate alignment and proper lits due to the close location tolerances required to mate the tabs and slots. Improper location can cause distortions of the delicate vanes, especially in small impellers. Moreover, the shroud or back plate may` not be closely iitting to the ends of the vanes' at various .parts because, for example, the shroud or back plate was not held firmly against the edges of the vanes when the tab was bent over to form the connection.

The foregoing and other disadvantages of present constructions of impellers of the above-mentioned type are Patented June 2l, 1966 iCC overcome, in accordance with the invention, by providing a novel and improved impeller structure comprising a back plate, a plurality of spaced-apart vanes extending from the back plate, preferably formed integrally therewith, and a small tab at the free ends of at least two of the vanes. A shroud positioned against the ends of the vanes is provided with slots receiving the tabs on the vanes, the tabs and slots having angularly related edges in interfering relation cooperating to urge the shroud toward the vanes and retain it thereon. In a preferred embodiment, the radially outermost edges of the tabreceiving slots are formed substantially parallel to the impeller axis of rotation and the corresponding edges of the tabs are formed to lie at an -angle to the axis, the said edges of the tab and the slots thus being angularly related, the outermost corners of the tabs overhanging the adjacent edges of the slots, and the outer corners of the slots When the shroud is released from twisting relative to the vanes, the vanes resile and bring the angularly related edges of the slots and tabs into tight engagement. Because of the angle between the cooperating tab edge and the slot edge, a sharp line of contact at the outer corner of the slot edge is provided to grip the edge of the tab. The angular relation of the tab edge provides a component of force urging the shroud into tight engagement against the edges of the vanes. As an-additional assembly step, though often unnecessary, the ends of the tabs may be bent over and heat staked to more firmly secure the shroud to the vanes.

There are several important advantages of the impeller structure of the invention over presently known impellers. For one thing, its construction is particularly well adapted to the use of plastics, although metals are lalso suitable and can be used to advantage. Plastics are desirable for their light weight, low cost, ease of handling and molding, and their ability to be heat formed at relatively low temperatures. Accordingly, the production and material costs of the impellers are considerably reduced. Further, the impeller structure provides an laccurate location of the blades relative to the shroud, inasmuch as the resilience of the vanes brings the tabs into tight engagement with the shroud slots. Additionally, the tight t isena'bled without the very close tolerances which would be required for accurately mating tabs and slots which .are initially formed to tit together at the same angle. Looseness of the connection between the vanes and the shroud is prevented, and inasmuch as the members are interconnected without adhesives, solder or the like, the possibility of unbalance being produced by unequal amounts of such substances being deposited at various annular locations on the impeller is avoided.

,The foregoing and other advantages of the impeller structure in accordance with the invention will be more readily apparent from a consideration of the following description of an exemplary embodiment, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a pictorial view of a fan utilizing the i-mpeller structure;

FIG. 2 is an end view of the impeller structure of y FIG. 1, several of the vanes .being omitted for improved illustration; v

FIG. 3 is a part-ial sectional side view of the impeller structure, the view being taken generally along the line 3-3 of FIG. 2 and in the direction of the arrows; and

FIG. 4 is a detail View in section taken adjacent the edge of a tab and slot by which the shroud is connected to the impeller vanes, the view being on a greatly enlarged scale relative to FIG. 3 and showing the encircled part of FIG. 3.

Referring to FIG. 1, the impeller structure is attached to a motor 12, the motor having electrical connectors 14 and 16 for connecting it to leads yfrom a power source. In the 4center of the impeller, as best shown in FIG. 2, is a small cover 18 which protects the internal struct-ure of the motor. The cover is held in place on the impeller by means of three tabs 20, 2,1 and 22 for-med l thereon and received in slots 23, 24 `and '25 formed in the central portion of the impeller back plate (described below). Detents 26, 27 and 28 formed between the cover 18 and the impeller .back plate retain the cover 18 from rotation. To install the cover, the tabs are lined up with the slots-and the cover pushed in and then twisted, by inserting a .suitable tool into recesses 29, 30 and 3'1 formed in the external central portion, until the detents are snapped into position.

Referring next to FIG. 3, the impeller includes a central annular rearwardly extending sleeve 40 which receives the rotating element of the motor 42, the sleeve being attached to the element by a suitable adhesive or by a press-fit or, preferably, both. T'he sleeve 40 is formed integrally with a back plate 44 of the impeller, which curves smoothly rearwardly and outwardly from the center.

Formed integrally with and extending at equally spaced locations from the back plate 44 is a series of impeller vanes 46. In the illustrated embodiment the vanes are angularly related and are .suitably curved so las .to provide centrifugal flow from the open forward ends to the radially outermost ends 46a thereof. It will be understood, of course, that various lforms of straight or `curved v vanes, which may be arranged to provide centripetal or axial ow, may also be used.

Attached to the ends 46h of the vanes 46 generally opposite the ends connected to the back plate 44 is a shroud 52 which is externally concave in shape `and extends entirely about the circumference of the impeller. The shroud 52 lits tightly against the ends 46b of the vanes, and in section taken along a radial plane through the impeller, as illustrated in FIG. 3, delfines with the back plate a gradually` constricted flow path.

The shroud 52 is connected to the ends 46h of the vanes 46 by integrally formed tabs 54 extending from and contiguous to the vanes and received in slots 56 formed in the shroud, as best shown in FIG. 4. The slots are ygenerally p-arallelogram-mic in plan, and the tabs are similarly shaped. In elevation, as shown in FIG. 4, the tabs and slots are tapered in a direction away from the vanes, and in end section, they have a uniform width.

The shroud is held tightly secured to the vanes by an interference fit created by angularly relating and dimensioning adjacent edges of the slot and tab. More particularly, the radially outermost narrow edge 54a of each tab is formed so as to lie in a plane, designated by the line Y-Y, disposed at an angle to a -plane X-X parallel to the axis of the impeller, and the outer corner S4b of the edge 54a is at a distance R' from the impeller axis. The adjacent edge v5601 of each slot 56 lies generally on a plane X-X parallel to the axis at a distance R therefrom. The dimension R' is somewhat greater than the dimension R, and thus, the tab corner 54b overhangs the slot edge 56a when the shroud is in place.

The outer corner 5612 of the slot 56a, it will be observed, is generally pointed and engages 54a of the tab. Further, the engagement point lies radially inwardly of the tab corner 54h, and the dimension to the tab at the engagement point, as the sl-ots and tabs are formed, is made-greater than the dimension to the slot edge corner 56h. Therefore, the tab is pressed under a degree of force against the slot corner 56h, and because of the force and the sharpness of the corner, an unexpe'ctedly strong connection is formed. Moreover, any movement of the shroud away from the ends of the vanes, because of the Iangular orientation of the tab edge 54a relative to lthe impeller axis, increases the holding force. The natural resiliency of `the blade and the angular relation of the tab also urge the shroud back into tight engagement with vthe vane edges should it start to move away.

To install the shroud on the impeller vanes, it Ais pressed against the vanes, with the slots approximately aligned with the mating tabs. The outer ends of the tabs are substantially smaller than the inner end of the slot and the initial alignment is made quite readily, To facilitate full engagement of the vanes and shroud and enable the outer corners 54b of the tabs to clear the interior end corner of the slots, a slight twist can be imparted to the shroud, thus, twisting the vanes and tab slightly and translating the edges 54a of the tabs radially inward. The shroud is pressed f ully onto the tabs, and when the twisting is released, the vanes and tabs will resile to produce the above-described inward urging of the shroud and the tight engagement and attachment of `the shroud to the vanes.

The force provided by the cooperation of the tabs and slots is surprisingly large, and is often sufficient to provide adequate retention of the shroud on the vanes in lactual use lof the impeller. Nevertheless, it is sometimes desirable to .heat stake the end of the tabs to ensure that lthe shroud will remain in place in the event that any sharp impact or unusual pressure conditions will not push or knock the shroud off.

The shroud attachment provided by cooperation between tabs and slots is not limited to the particular edges of the above-described embodiment, and other adjacent edges of the tab and slot can be angularly related and dimensioned to afford a similar attachment. Additionally, a back-plate of an impeller can be secured to vanes by 4the same expedient.

It will be understood that the above-described embodiment of the invention is merely exemplary and that those skilled in the art will be able to make many modications and variations therein without departing from the spirit and scope of the invention. Accordingly, all such modications are intended to be within the scope of the invention as defined in the appended claims.

I claim:

1. An impeller assembly comprising a rst annular member, a plurality of vanes, each of said vanes being connected a-t one edge of said rst member and extending outwardly therefrom, a tab extending from an opposite edge of each of at least two of said vanes and contiguous thereto, and a second annular member having slots formed therein receiving said tabs and closely fitting the said opposite edges of said vanes, the slots and tabs being of generally parallelogrammic shape in the plane of the surface of said second annular member and each slot and tab having .a longel. axis in said plane aligned at a substantial angle to a radial plane of the impeller intersecting them, each of said tabs having its radially outermost edge angularly disposed relative to the axis of the impeller with the outer corner of said -*angularly disposed edge extending beyond the outer surface of said second annular member and being disposed at a greater distance from the impeller axis than the -outermost edge of the slot in said second annular member, each of said slots having its radially outermost edge disposed substantially parallel to the impeller axis and dening with the outer surface .of said second annular member a sharp corner, and said sharp corner tightly engaging said angularly disposed tab edge.

2, An impeller assembly comprising a rst annular 5 member, a plurality of vanes, each of said vanes being connected at one edge to said rst member and extending outwardly therefrom, a tab extending from an opposite edge of each of at least two of said vanes and contiguous thereto, and a second annular member having slots formed therein receiving said tabs and closely tting the said opposite edges of said vanes, the second annular member curving outwardly from its radially inner-most edge where a tangent thereto is substantially parallel to the impeller axis to its outermost edge where a tangent thereto forms a substantial angle to the irnpeller axis, therslots and tabs being of generally parallelogrammic shape in the plane of the surface of saidsecond annular member and each slot and tab being aligned at a substantial angle to a radial plane of the impeller intersecting them, each of said tabs having its radially outermost edge angularly disposed relative to the axis -of the impeller with -the outer corner of said .angularly disposed edge extending beyond the outer surface of said second annular'member and being disposed at a greater distance from the impeller axis than the outermost edge of the slot in said second annular member, each of said slots having its radially outermost 6 edge disposed substantially parallel to the impeller axis and defining with the outer surface of said second annular member a sharp corner which is in engagement with said angularly disposed tab edge, the vanes being resiliently deflectable of facilitate the receiving of lthe tabs.

thereon in the slots of the second annular member by a twisting motion elective to translate said radially outermost tab edges inwardly `toward the impeller axis.

References Cited by the Examiner UNITED STATES PATENTS 2,473,185 6/1949 Weiss 103-115 2,701,531 2/ 1955 English 103-115 2,712,285 7/1955 Jandasek 10S-115 2,932,445 4/ 1960 Hathaway 230-l34 2,991,004 7/1961 Denbo et al. 103-114 FOREIGN PATENTS 811,414 4/ 1959 Great Britain.

SAMUEL LEVINE, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. AN IMPELLER ASSEMBLY COMPRISING A FIRST ANNULAR MEMBER, A PLURALITY OF VANES, EACH OF SAID VANES BEING CONNECTED AT ONE EDGE OF SAID FIRST MEMBER AND EXTENDING OUTWARDLY THEREFROM, A TAB EXTENDING FROM AN OPPOSITE EDGE OF EACH OF AT LEAST TWO OF SAID VANES AND CONTIGUOUS THERETO, AND A SECOND ANNULAR MEMBER HAVING SLOTS FORMED THEREIN RECEIVING SAID TABS AND CLOSELY FITTING THE SAID OPPOSITE EDGES OF SAID VANES, THE SLOTS AND TABS BEING OF GENERALLY PARALLELOGRAMMIC SHAPE IN THE PLANE OF THE SURFACE OF SAID SECOND ANNULAR MEMBER AND EACH SLOT AND TAB HAVING A LONGER AXIS IN SAID PLANE ALIGNED AT A SUBSTANTIAL ANGLE TO A RADIAL PLANE OF THE IMPELLER INTERSECTING THEM, EACH OF SAID TABS HAVING ITS RADIALLY OUTERMOST EDGE ANGULARLY DISPOSED RELATIVE TO THE AXIS OF THE IMPELLER WITH THE OUTER CORNER OF SAID ANGULARLY DISPOSED EDGE EXTENDING BEYOND THE OUTER SUR- 